The Bloomberg administration is scrambling to gather enough City Council votes to enact the mayor’s final plan for reshaping New York City’s skyline with a new generation of ever-taller skyscrapers.

The proposal would rezone a 73-block area surrounding Grand Central Terminal and allow the kind of sleek skyscrapers the administration says are necessary for the city’s premier office district to stay competitive with London and other world capitals. In some locations, developers would be able to erect towers more than twice the size of current buildings, which would cast the Chrysler Building, the Waldorf-Astoria and St. Bartholomew’s Episcopal Church into shadow.

Many leading figures in the real estate industry, and many construction unions, support the plan, as does the Regional Plan Association, an influential private research organization. But a broad array of Manhattan community boards, preservationists and elected officials contend that the rezoning has been rushed, and could overwhelm a neighborhood whose streets are already congested and subway lines overcrowded.

The City Council will have its first hearing on the proposal on Tuesday, and is expected to vote on it within the next month. In pushing through more than 125 rezoning proposals throughout the city, Mayor Michael R. Bloomberg has usually overcome the obstacles inherent in passing such changes. But with fewer than 75 days left in his term, the political dynamics have changed. The mayor’s clout with the Council is fading. His onetime ally, Christine C. Quinn, the Council speaker, is also a lame duck.

As a result, Daniel R. Garodnick, a council member whose district includes much of the area around Grand Central, and who is a candidate for speaker, has emerged as a pivotal figure in the fate of the proposal. Other members of the Council are expected to take their cues from him, and right now Mr. Garodnick is not satisfied.

“While the proposal has merit,” Mr. Garodnick said, “it remains incomplete, and despite our best efforts to nail down solutions to outstanding issues, we are running out of time. If we feel we can’t do it within the land use clock we will have no hesitation taking this up with the next administration.”

Mr. Garodnick suggested that the Council might be able to pass a modest version of the rezoning in the next four weeks and then take it up in a more expansive way next year.

Both the Democratic and Republican candidates for mayor, Bill de Blasio and Joseph J. Lhota, generally support rezoning the district. But like Mr. Garodnick, Mr. de Blasio has faulted the administration for a lack of planning for new residents and office workers and for setting the price for development rights too low, at $250 per square foot.

“If these issues can’t be resolved adequately now, in this Council with this administration, then I think we should press the pause button and address these issues in the context of a new rezoning plan next year,” Mr. de Blasio said.

Robert Steel, the deputy mayor for economic development, insists that the administration is making headway.

Photo

Michael R. Bloomberg’s plan would affect a 73-block area.Credit
Ángel Franco/The New York Times

“We’re optimistic,” Mr. Steel said. “We’ve been working our way through all the constituents, the developers, the religious institutions, preservationists. It’s taken a long time, but it’s exciting.”

In recent days, Mr. Steel has conferred with council members, State Senators Brad Hoylman and Liz Krueger, and Lola Finkelstein, who heads a task force for four community boards.

Mr. Steel has also met with Peter Ward, the president of the powerful hotel workers’ union. Mr. Ward opposes the rezoning because it would not require hotel plans to go through a special approval process that typically allows the union to secure guarantees on wage levels and other workplace issues. Mr. Ward is sending more than 100 union members to the Council hearing on Tuesday.

The Bloomberg administration is playing other cards in its bid to nail down support for the rezoning. On Tuesday, it will announce plans for a $100 million bond that will pay for improvements to subway stairwells and platforms below Grand Central. Last Thursday, the administration unveiled proposals to create a public plaza south of Grand Central and pedestrian balconies along the Grand Central viaduct.

But so far, opponents have not been persuaded.

David W. Levinson, a developer whose project would benefit from the rezoning, said he was worried about the prospects for the proposal, which has been driven by developers’ desire for a measure of certainty.

Mr. Levinson controls an aging office building at 425 Park Avenue, between 55th and 56th Streets. He has long planned to demolish the building in order to build a modern, high-end office tower for hedge funds and private equity firms. The building was erected before the adoption of the current zoning, which no longer permits towers of its size. If Mr. Levinson razed it, he could erect a tower only about four-fifths as large. But if he retained 25 percent of the existing steel structure, he could build another the same size, under the current zoning.

Back in 2010, Mary Ann Tighe, then head of the Real Estate Board of New York, tried to broker a solution. She asked Amanda Burden, director of the city’s Planning Department, to allow developers like Mr. Levinson to build towers of the same size without incorporating the old steel structure. Such “grandfathering,” she argued, would encourage construction of up-to-date towers in the Grand Central area, where many of the buildings were more than 70 years old and increasingly unattractive to corporate tenants. But Ms. Burden rejected the idea.

Then, in June 2012, she released an early version of the plan now on the table, proposing to rezone an area stretching from 39th Street to 57th Street, between Third and Fifth Avenues, for substantially taller buildings. It was far more ambitious than the grandfathering idea the industry had pushed. To keep the process moving forward, the Bloomberg administration has made a number of concessions to real estate interests. Under certain circumstances, new buildings can now include apartments, and some towers can be built on smaller sites than originally envisioned. Also, St. Patrick’s Cathedral and St. Bart’s would be permitted to transfer unused development rights to more sites than are currently permitted.

The initial rezoning plan contained a sunrise provision in which developers would have to wait five years before they could start building, to reduce competition with other current city-sponsored developments, like the Hudson Yards and the World Trade Center.

But the administration has since revised the rezoning plan to allow Mr. Levinson and a second developer, SL Green, to proceed more quickly. SL Green owns a block bound by 42nd and 43rd Streets, between Madison and Vanderbilt Avenues. The company wants to demolish the three buildings on the site — none are taller than 20 stories — to build a 65-story, 1.6-million-square-foot tower, to be known as 1 Vanderbilt.

City officials and proponents of the project say that the new zoning would require them to build more than $100 million in improvements to the subway entrances and platforms, as well as a public space inside the building, with a large train-arrival board and a new entrance to Grand Central Terminal.

But opponents say the administration’s proposal, even with myriad revisions, remains deeply flawed and worthy of continuing review.

A version of this article appears in print on October 22, 2013, on page A18 of the New York edition with the headline: Clock Ticking, Bloomberg Seeks Council Approval of East Midtown Rezoning Plan. Order Reprints|Today's Paper|Subscribe